Dr. Qian's long-term objective is to contribute to a better understanding of kidney disease pathophysiology, especially the vascular complications of autosomal dominant polycystic kidney disease (ADPKD). Her aim, over five-years, is to become a well-trained independent physician scientist with advance theoretical and technical knowledge in genetics and molecular and cellular biology through the implementation of this proposal. The candidate's mentor, Dr. Torres, is an expert in clinical and vascular aspects of ADPKD and her co-mentor, Dr. Harris, brings a detailed knowledge of ADPKD genetics. The third mentor, Dr. Farrugia, is an expert in Ca2+ homeostasis and will provide valuable guidance for that part of the proposal. The particular focus of this proposal is to study the role of the ADPKD proteins, polycystin-1 and -2 in the vasculature and to determine if defects in these proteins are directly related to the vascular manifestations and hypertension associated with ADPKD. Preliminary studies have indicated that the polycystins are expressed in vascular smooth muscle cells (VSMC) and that they interact as a part of a polycystin complex that may play a role in maintaining intracellular Ca2+ The first two Specific Aims of the proposal are to examine the consequences of mutation to the murine Pkdl and Pkd2 genes, and over expression of the human protein in mouse, on the characteristics of VSMCs. These will be analyzed in vitro, as cultured VSMCs and in vivo, by study of the ultrastructure of the vasculature in the mouse mutants. Specific Aim 3 will identify components of a VSMC polycystin complex using imaging methods, co-immunoprecipitation and the yeast two- hybrid technique. The results of these studies will allow a VSMC polycystin complex to be defined and comparison made to corresponding complexes in epithelial cells. The final part of the proposal (Specific Aim 4) will examine the role of the polycystins in maintaining intracellular calcium homeostasis and analyze the consequences of Pkd1/2 mutation. Overall, the results from these studies should provide a clearer view of the function of the polycystins in VSMCs and the likely role that loss of these proteins may play in the vascular abnormalities and hypertension associated with ADPKD. This information will provide the basis for designing rational therapies for the treatment of these complications. This period of laboratory based study, plus the formalized career development program, is designed to train the candidate as a physician scientist with a unique expertise in vascular aspects of ADPKD.